This application claims the benefit of Korean Patent Application No. 2003-2910, filed Jan. 16, 2003, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates, in general, to a high frequency generator and, more particularly, to a noise filter for a high frequency generator.
2. Description of the Related Art
High frequency generators, such as magnetrons, klystrons, traveling wave tubes and semiconductor devices, are utilized in various fields. A high frequency generator mainly employs a noise filter to prevent undesired leakage of high frequency energy. The leakage of high frequency energy causes noise in electronic devices, such as radios and televisions. For this reason, it is important to prevent leakage of high frequency energy from high frequency generators. Generally, a noise filter includes inductance elements such as choke coils, capacitors and a shielding casing, and is connected to an electric conductor used to supply power.
FIG. 1A is a partially sectional view and FIG. 1B is a top view of a conventional noise filter for a high frequency generator which are disclosed in Korean Non-examined Patent Publication No. 10-1999-72650. As shown in FIGS. 1A and 1B, a noise filter 120 is disposed under a magnetron 100. Inside a filter casing 144 of the noise filter 120, choke coils 154, each including a core inductor 150 and an air-core inductor 152 connected in series to each other, are disposed. The core inductors 150 have high-frequency energy absorbing members 148 inserted therein, while the air-core inductors 152 do not have the high-frequency energy absorbing members 148 therein. The core inductors 150 are connected to a condenser 158. The air-core inductors 152 are connected to a stem 156 through stem terminals 156a and 156b. 
Generally, a core inductor may reduce noise in a frequency band below 400 MHz by regulating a number of winding turns of the core inductor. An air-core inductor may reduce noise in a frequency band ranging from 700 MHz to 1000 MHz by regulating a number of winding turns of the air-core inductor. In the conventional noise filter shown in FIGS. 1A and 1B, each of the core inductors 150 and each of the air-core inductors 152 are connected in series to each other, and sectional areas of the high-frequency energy absorbing members 148 are sized so that noise in a frequency band ranging from 400 MHz to 1000 MHz is reduced.
However, in a conventional noise attenuation apparatus such as the above described noise filter, a noise attenuating frequency band is limited to 400 MHz to 1000 MHz. Thus, a noise attenuation effect may not be expected for noise in a frequency band ranging from 30 MHz to 400 MHz.
Accordingly, it is an aspect of the present invention to provide a noise filter for a high frequency generator, having varied spacing between winding turns of core inductors provided in a choke coil of the noise filter, thereby maximizing a frequency band in which noise is attenuated.
Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
The foregoing and/or other aspects of the present invention are achieved by providing a noise filter for a high frequency generator including a choke coil having a first winding unit having a first spacing between winding turns thereof, a second winding unit having a second spacing between winding turns thereof and a third winding unit having a spacing the same as the first spacing between winding turns thereof. The first, second, and third winding units are connected in series to each other. The high frequency generator also includes a high-frequency energy absorbing member inserted into the choke coil.
According to an aspect of the invention the high-frequency energy absorbing member is made of any one selected from a group consisting of iron oxide, tin alloy and ferrite.
According to an aspect of the invention, the high frequency absorbing member includes a sectional area to attenuate noise in a frequency band ranging from 30 MHZ to 1000 MHz.